1. Field of the Invention
The present invention relates generally to a surface mount antenna apparatus adapted for a wireless terminal and, more particularly, to a surface mount antenna apparatus having a triple land structure, which does not need an additional matching circuit, and is capable of generating a strong electromagnetic field between an antenna and a ground area, thus improving radiation performance.
2. Description of the Related Art
Recently, due to the development of communication and broadcasting technology and the expansion of service, small, cheap, and multi-functional communication terminals and broadcast receivers have been proposed. Thus, antennae used for the communication terminals and broadcast receivers are designed to contribute to the small, cheap, and multi-functional structure. One of the types of antenna that are suitable for reducing the size and cost of a terminal is a chip antenna mounted on a PCB (Printed Circuit Board) using surface mount technology.
In this case, the surface mount technology is a method of mounting a lead of a device to the surface of a PCB using a soldering material or the like, without inserting the lead into a hole of the PCB. A device which is formed to be suitable for this mounting method is called an SMD (Surface Mount Device).
Such a surface mount antenna is mounted on a land structure which is formed on a PCB. Thus, in order for the antenna to have proper efficiency at a corresponding terminal, radiation characteristics of the antenna itself, electromagnetic characteristics between the antenna and the land structure, and impedance matching between the antenna and a reception circuit must be appropriately set.
Herein, an apparatus including a PCB, a land structure, and an antenna is defined as an antenna apparatus.
FIG. 1 is a perspective view of a conventional surface mount antenna apparatus, and FIG. 2 is a view showing a land structure of the conventional surface mount antenna apparatus. The conventional surface mount antenna apparatus will be described with reference to FIGS. 1 and 2.
As shown in FIGS. 1 and 2, a PCB 10 is divided into a ground electrode 11 and a non-grounded area 12, and an antenna 20 is mounted on the non-grounded area 12.
In order to stably mount the antenna 20 on the non-grounded area 12, two land pads LP1 and LP2, to be connected to two pads which are provided on the lower surface of the antenna 20, are provided on the non-grounded area 12. The land pads LP1 and LP2 are provided at positions corresponding to the two pads provided on the lower surface of the antenna 20 in such a way as to be spaced apart from the ground electrode 11 by a predetermined interval. In this case, one of the two land pads is connected to a signal line.
Further, the antenna apparatus must be provided with a matching circuit 15 to match impedance between the antenna 20 and a reception circuit, thus preventing signal loss.
In the conventional surface mount antenna apparatus, the antenna mounted on the land structure has a helical structure in order to realize miniaturization, as shown in FIG. 1.
The antenna 20 of FIG. 1 includes a dielectric block 20A having a lower surface, an upper surface, and a plurality of side surfaces. The antenna 20 also includes a feeding electrode 21 and a ground electrode 22 which are provided on the lower surface of the dielectric block 20A. Further, a helical radiation electrode 23 comprising a coil is provided on the upper surface, side surfaces, and lower surface of the dielectric block 20A.
Generally, the helical antenna mounted on the land structure having the two land pads LP1 and LP2 has a ground electrode 11 only at the position where the land pad LP1 connected to the matching circuit 15 is located. In this case, the antenna is operated with a radiation mechanism similar to a mono-pole antenna in a normal operational mode.
Therefore, in the case of having peripheral ground conditions shown in FIGS. 1 and 2, the ground electrode 11 having a spacing distance of λ/8 or higher of an operating frequency must be provided so as to achieve a radiating efficiency of 50% or higher of the antenna's theoretical potential.
Such an operating principle is understood to be similar to the phenomenon occurring when a dipole or monopole antenna is brought horizontally near a PEC. Thus, in view of the characteristics of the antenna, the non-grounded area 12 must be considerably larger than the antenna. That is, when the non-grounded area 12 is smaller than a preset size, the performance of the antenna is considerably deteriorated. Further, since a radiation unit is provided with the matching circuit for impedance matching, the loss of the antenna may be increased and impedance matching is difficult.
As described above, the conventional surface mount antenna apparatus is constructed so that the antenna 20 mounted on the PCB 10 has a helical structure, and the non-grounded area 12 is much larger than the antenna 20, to an extent such that it is several times as large as the antenna 20, so as to allow the helical antenna apparatus 20 to exhibit efficient performance. Thus, a large space must be secured to mount the antenna 20 on the PCB 10, so that it is difficult to reduce the size of an associated terminal.
Further, since an additional matching circuit 15 is required, the circuit construction is complicated, and manufacturing costs are increased, thus increasing the cost of a terminal having such an antenna apparatus.